Such a layer system has a substrate comprising a metal alloy based on nickel or cobalt. Such products are used especially as a component of a gas turbine, in particular as gas turbine blades or heat shields. The components are exposed to a hot gas flow of aggressive combustion gases. They must therefore be able to withstand heavy thermal loads. It is furthermore necessary for these components to be oxidation- and corrosion-resistant. Especially moving components, for example gas turbine blades, but also static components, are furthermore subject to mechanical requirements. The power and efficiency of a gas turbine, in which there are components exposable to hot gas, increase with a rising operating temperature.
In order to achieve a high efficiency and a high power, those gas turbine components which are particularly exposed to high temperatures are coated with a ceramic material. This acts as a thermal insulation layer between the hot gas flow and the metallic substrate.
The metallic base body is protected against the aggressive hot gas flow by coatings. In this context, modem components usually comprise a plurality of coatings which respectively fulfill specific functions. The system is therefore a multilayer system. Since the power and efficiency of gas turbines increase with a rising operating temperature, attempts have continually been made to achieve a higher performance of gas turbines by improving the coating system.
EP 0 944 746 B1 discloses the use of pyrochlores as a thermal insulation layer. The use of a material as a thermal insulation layer, however, requires not only good thermal insulation properties but also good bonding to the substrate.
EP 0 992 603 A1 discloses a thermal insulation layer system of gadolinium oxide and zirconium oxide, which is not intended to have a pyrochlore structure.